Replication

Overview

Replication is the process of creating a copy of a subset of data and storing it on another DDF or ION based System. Data can be pulled from a remote DDF and saved to another DDF or ION system. Metacards produced by replication are marked with a "Replication Origins" attribute and a tag of "replicated". Replication will automatically start transferring data once an admin creates a replication configuration.

Known Issues, Limitations, and Assumptions

Replication is still at an early stage in its lifecycle, so there are a few details that the user should be aware of.

Fanout Proxies

Replicating from a DDF system that is configured as a Fanout Proxy will result in the replication of records from sources configured in that system.

Replicating to a DDF system that is configured as a Fanout Proxy will result in the replication of records only to the fanout and not its sources.

Connected Sources

Replicating from a DDF sytem that is configured with Connected Sources will result in the replication of records from the Connected Sources in addition to any local records.

Derived Resources

Derived resources, from products such as NITFs, will not be replicated.

Docker Compose Deployment

Prerequisites

Replication is deployed as a docker stack in a docker swarm. So, before deploying replication, you need a running docker instance with an initialized swarm. Once you have a swarm running you can configure it for replication with the following steps.

Configuration

The configuration that replication uses needs to be populated in docker config

Config Name	Description
replication-spring-config	The spring-boot application.yml for replication. Example below.

Example replication-spring-config

logging:
  level: 
  #You can adjust the log levels of a package or class in this section 
    root: INFO
    org.apache.cxf.interceptor.LoggingOutInterceptor: WARN
    org.apache.cxf.interceptor.LoggingInInterceptor: WARN
    javax.xml.soap: ERROR
spring:
  data:
    solr:
    #This is the URL the replication service will use to communicate with solr.
    #As long as you use the docker compose file you won't need to change this.
      host: http://replication-solr:8983/solr 
  profiles.active: Classic
replication:
  #This is the number of seconds between each replication, lower it if you're going to be testing.
  period: 300
  #Timeouts for calls to sites
  connectionTimeout: 30
  receiveTimeout: 60
  #The ID of the local site. All replications will go to/from this site. Direction will be determined 
  #by the type and kind of site being replicated with. This field needs to be set, and a site with
  #this ID needs to be saved before any replication will take place. 
  localSite: some-unique-id-1234
  #The remote sites to handle replication for, remove this to handle replication for all sites.
  sites:
  - site1
  - site2
  
# Exposes metrics
management:
  endpoint:
    metrics:
      enabled: true
    prometheus:
      enabled: true
  endpoints:
    web:
      exposure:
        include: 'prometheus,metrics,health,info'
  metrics:
    export:
      prometheus:
        enabled: true

To create a docker config use the config create command, which uses this syntax: docker config create <CONFIG_NAME> <FILE_DIRECTORY>

Example: docker config create replication-spring-config replication/configs/application.yml

Profiles

Replication can be run with one of two profiles. You can specify which profile to use in the 'spring.profiles.active' property as demonstrated in the example above. "Classic" will use the classic monolithic implementation. "Ion" will use the new scalable, cloud oriented implementation.

Metrics

Replication supports reporting metrics through Micrometer. Prometheus is used as the metrics collection platform. The replication-spring-config provides example configuration for exposing metrics from within the application.

Grafana

A Grafana dashboard grafana-dashboard.json is provided, which can be imported into Grafana.

Secrets

Replication requires certs and ssl configurations in order to talk with remote DDF based systems. This information is stored in docker secrets.

Secret Name	Description
replication-truststore	A truststore to use for TLS
replication-keystore	A keystore for this system to use TLS
replication-ssl	SSL properties for TLS including passwords for the truststore and keystore

Example replication-ssl

javax.net.ssl.trustStorePassword=changeit
javax.net.ssl.trustStoreType=jks
javax.net.ssl.keyStorePassword=changeit
javax.net.ssl.keyStoreType=jks
javax.net.ssl.certAlias=localhost

Only the properties that differ from the defaults above need to be specified in replication-ssl

To add a docker secret use the secret create command, which uses this syntax: docker secret create <SECRET_NAME> <FILE_DIRECTORY>

Example: docker secret create replication-truststore replication/secrets/truststore.jks

Running

Running the stack will start up a solr service and the replication service.

docker stack deploy -c docker-compose.yml repsync

Adding Replication Configuration

Replication can be configured by using the Solr rest endpoint.

curl -H "Content-Type: application/json" \
-d @/path/to/json/config/file.json \
http://localhost:8983/solr/<target-core>/update?commitWithin=1000

Types and Kinds of sites

Sites can be of different types and kinds. The type and kind of the remote site (the one that's not the local site) will determine whether the replication is a push, pull, harvest, or both push and pull.

Site Type	Site Kind	Replication Direction
DDF	TACTICAL	BIDIRECTIONAL
DDF	REGIONAL	HARVEST
ION	TACTICAL	BIDIRECTIONAL
ION	REGIONAL	PUSH

Directions

Here's how the various replication directions are defined: PUSH - Send information to the remote site to be stored. PULL - Retrieve information from the remote site and store it locally. BIDIRECTIONAL - Perform both a push and a pull. HARVEST - Similar to a pull but harvesting will ignore updates and deletes on replicated information.

Adding Site Example

Create a json file with site descriptions like the example below and you can use the following curl command to save those sites for replication to use. Example sites.json

  [
      {
        "version": 1,
        "id": "some-unique-id-1234",
        "name": "RepSync-Node1",
        "description": "Replication Site 1",
        "url": "https://host1:8993/services/",
        "type": "DDF",
        "kind": "TACTICAL",
        "polling_period": 600000,
        "parallelism_factor": 1
       },
      {
        "version":1,
        "id": "another-unique-id-5678",
        "name": "RepSync-Node2",
        "description": "Replication Site 2",
        "url": "https://host2:8993/services",
        "type": "DDF",
        "kind": "TACTICAL",
        "polling_period": 600000,
        "parallelism_factor": 1
      }
   ]

curl -H "Content-Type: application/json" \
-d @sites.json \
http://localhost:8983/solr/replication_site/update?commitWithin=1000

Adding Replication Filters Example

Create a json file with filter descriptions like the example below and you can use the following curl command to save those filters for replication to use. Example filters.json

   [
      {
        "name":"pdf-harvest",
        "site_id":"remote-site-id",
        "filter":"\"media.type\" like 'application/pdf'",
        "suspended":false,
        "priority": 0,
        "id":"unique-filter-id-98765",
        "version":1
      }
    ]

curl -H "Content-Type: application/json" \
-d @filters.json \
http://localhost:8983/solr/replication_filter/update?commitWithin=1000

Removing Replication Configuration

Example removing all sites with the name 'Test'

curl -X POST \
  'http://localhost:8983/solr/replication_site/update?commit=true' \
  -H 'Content-Type: application/xml' \
  -d '<delete><query>name_txt:Test</query></delete>'

Example removing all sites

curl -X POST \
  'http://localhost:8983/solr/replication_site/update?commit=true' \
  -H 'Content-Type: application/xml' \
  -d '<delete><query>*:*</query></delete>'

Try it out

You can try replication for yourself using the steps below as a high level overview. Details on how to complete steps related to setting up replication can be found above, starting with "Docker Compose Deployment".

Make sure docker is up and running. Start up a docker swarm if you haven't already.
Create docker config
Create docker secrets
Deploy stack
Create two sites, Both as REGIONAL DDFs, with URLs pointing to running DDF instances.
The remote site (The site that isn't the local site) will be your source of data. Upload test data to the source site if it has none.
Create filter. The "site_id" should match the ID of remote site. The filter can be changed to something like ""title" like 'test'" or ""title" like '*'" to replicate everything.
execute docker service logs -f repsync_ion-replication to view the logs and wait for replication to occur. Once you start seeing logs check the local site to see the data start coming in.

paouelle/replication